Title should not overflow the content area
A few things to check for:
Non-breaking text in the title, content, and comments should have no adverse effects on layout or functionality.
Check the browser window / tab title.
This post has no title, but it still must link to the single post view somehow.
This is typically done by placing the permalink on the post date.
This post has many categories.
Nested and mixed lists are an interesting beast. It's a corner case to make sure that
Lists within lists do not break the ordered list numbering order
Your list styles go deep enough.
Ordered - Unordered -...